Prismatic storage battery or cell with flexible recessed portion

ABSTRACT

A battery includes a cell casing that has recessed portion on a major surface of the casing, the recessed portion being substantially planar and bordering a remainder of the major surface at ridge portions on at least three sides of the recessed portion, whereby the recessed portion, the ridge portions, and the remainder of the major surface cooperate under an increase of gauge pressure to cause a plane defined by a boundary between the ridge portions and the remainder of the major surface to move.

RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.61/125,281, filed on Apr. 24, 2008. The entire teachings of the aboveapplication are incorporated herein by reference.

INCORPORATION BY REFERENCE

U.S. Patent Application No. 60/936,825, filed on Jun. 22, 2007;International Application No. PCT/US2007/014591, filed on Jun. 22, 2007;U.S. Provisional Application No. 60/717,898, filed on Sep. 16, 2005;U.S. patent application Ser. No. 11/474,081, filed on Jun. 23, 2006;U.S. patent application Ser. No. 11/474,056, filed on Jun. 23, 2006;U.S. patent application Ser. No. 11/485,068, filed on Jul. 12, 2006;U.S. patent application Ser. No. 11/486,970, filed on Jul. 14, 2006;U.S. patent application Ser. No. 11/821,102, filed on Jun. 21, 2007;U.S. Provisional Application No. 61/125,285, filed on Apr. 24, 2008,entitled “Lithium-Ion Secondary Battery;” and U.S. ProvisionalApplication No. 61/125,327, filed on Apr. 24, 2008, entitled “Method ToImprove Overcharge Performance Of Lithium-Ion Cells with CID,” bothfiled on even date herewith, are all incorporated herein by reference intheir entirety.

BACKGROUND OF THE INVENTION

Li-ion batteries in portable electronic devices typically undergodifferent charging, discharging and storage routines based on their use.Batteries that employ Li-ion cell chemistry may produce gas when theyare improperly charged, shorted or exposed to high temperatures. Thisgas can be combustible and may compromise the reliability and safety ofsuch batteries. A current interrupt device (CID) is typically employedto provide protection against any excessive internal pressure increasein a battery by interrupting the current path from the battery whenpressure inside the battery is greater than a predetermined value.

However, even in the absence of excessive internal pressure that woulddiminish performance or cause safety concerns, li-ion batteries undergoincreased internal pressure during recharging. In prismatic cells,increased internal pressure causes the cell casing to flex. Dependingupon the makeup and amount of electrode and electrolyte material withina cell casing, such as a 183665 prismatic cell casing, an outsidediameter of about 18.02 mm can increase during recharging by over onemillimeter, to about 19.5 mm. Use requirements of many battery types,including prismatic cells, often limit the space available for expansionduring charge cycles, thereby restricting the types of batteriesemployed, their capacity, or the patterns of their use (e.g., removalfrom devices during charging).

Therefore, a need exists for a cell casing that significantly reduces oreliminates the above-mentioned problems.

SUMMARY OF THE INVENTION

The present invention generally relates to a battery cell casing thatincludes a recessed portion at a major surface that flexes during cyclicrecharging. The invention also relates to batteries that employ thebattery cell casing.

In one embodiment, the present invention is directed to a battery cellcasing having a recessed portion on a major surface of the casing, therecessed portion being substantially planar and bordering a remainder ofthe major surface at ridge portions on at least three sides of therecessed portion, whereby the recessed portion, the ridge portions, andthe remainder of the major surface cooperate under an increase of gaugepressure to cause a plane defined by a boundary between the ridgeportions and the remainder of the major surface to move.

In another embodiment, the invention is directed to a battery thatincludes a first terminal in an electrical communication with a firstelectrode of the battery and a second terminal in electricalcommunication with a second electrode of the battery. The battery alsoincludes a battery can having a cell casing and a lid which are inelectrical communication with each other, the battery being electricallyinsulated from the first terminal. The cell casing has a recessedportion on a major surface of the casing, the recessed portion beingsubstantially planar and bordering a remainder of the major surface atridge portions on at least three sides of the recessed portion, wherebythe recessed portion, the ridge portions, and the remainder of the majorsurface cooperate under an increase of gauge pressure to cause a planedefined by a boundary between the ridge portions and the remainder ofthe major surface to move.

In another specific embodiment, the first electrode of the battery is acathode that includes an active cathode material, wherein the activecathode material includes a lithium cobaltate.

In another specific embodiment, the first electrode of the battery is acathode that includes an active cathode material, wherein the activecathode material includes a mixture of:

-   -   a) a lithium cobaltate; and    -   b) a manganate spinel represented by an empirical formula of        Li_((1+x1))(Mn_(1−y1)A′_(y2))_(2−x2)O_(z1)        -   wherein:            -   x1 and x2 are each independently equal to or greater                than 0.01 and equal to or less than 0.3;            -   y1 and y2 are each independently equal to or greater                than 0.0 and equal to or less than 0.3;            -   z1 is equal to or greater than 3.9 and equal to or less                than 4.2; and            -   A′ is at least one member of the group consisting of                magnesium, aluminum, cobalt, nickel and chromium,                wherein the lithium cobaltate and the manganate spinel                are in a weight ratio of lithium cobaltate:manganate                spinel between about 0.95:0.05 and about 0.6:0.4.

In yet another specific embodiment, wherein the active cathode materialof the battery includes a mixture that includes:

-   -   a) Li_(1+x8)CoO_(z8); and    -   b) Li_((1+x1))Mn₂O_(z1) wherein:        -   x1 is equal to or greater than 0.01 and equal to or less            than 0.3; and        -   z1 is equal to or greater than 3.9 and equal to or less than            4.2,            wherein LiCoO₂ and Li_((1+x1))Mn₂O_(z1) are in a weight            ratio of lithium cobaltate:manganate spinel between about            0.95:0.05 and about 0.6:0.4.

In yet another specific embodiment, at least a portion of the batterycan is at least a component of the second terminal, or is electricallyconnected to the second terminal, and further includes a lid welded onthe cell casing and at least one current interrupt device in electricalcommunication with either of the first or second electrodes. The currentinterrupt device includes a first conductive plate having a frustum, thefrustum including a first end and a second end having a diameter lessthan that of the first end, and an essentially planar cap sealing thesecond end of the frustum, wherein the basis proximal to the battery canand the essentially planar cap is distal to the battery can. The secondconductive plate is an electrical communication with the firstconductive plate and with either of the first and second electrodes, andthe weld connecting the first and second plate structures when a gaugepressure between the plates is in a range of between about 4 kg/cm² and9 kg/cm². The cell casing also includes at least one venting means,through which gaseous species inside the battery exit when a gaugepressure is in a range of between about 10 kg/cm² and about 20 kg/cm².

The present invention has many advantages. For example, the recessedportion, in combination with the remainder of the major surface of thebattery cell casing, can flex as a consequence of increasing gaugepressure caused by, for example, normal recharging of a battery, such asa lithium ion-type battery, employing a cell casing of the invention.The recessed portion, in combination with the ridge portions and theremainder of the major surface, according to the invention, providessome additional structural rigidity to the battery cell casing and, as aconsequence, significantly reduces any increase in width of the cellcasing from that which would occur without the presence of the recessedportion. It has been discovered, however, that retention of flexibilityand consequent increase in volume during recharging cycles, albeit inreduced amounts, essentially preserves battery life, such as inlithium-ion batteries, relative to batteries where no change in internalvolume is permitted during recycling. Therefore, battery cycle life canessentially be preserved while significantly reducing volume metricrequirements, thereby increasing the flexibility and types of use towhich rechargeable batteries can be put.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view in perspective of a prismatic battery of oneembodiment of the invention.

FIG. 2A is a top view of a cell casing of the invention.

FIG. 2B is a side view of the cell casing of FIG. 2A taken along lineBB.

FIG. 2C is a section view of the cell casing of FIG. 2A taken along lineCC.

FIG. 2D is a detail of a portion of FIG. 2C.

FIG. 3A is an arbor employed in one embodiment to form the cell casingshown in FIGS. 2A through 2D.

FIG. 3B is a punch employed in one embodiment to form the cell casingshown in FIGS. 2A through 2D;

FIG. 4A is a section view of the wall of the cell casing in a non-flexedposition.

FIG. 4B is a section view of the wall of the cell casing in a flexedposition.

FIG. 4C is a section view of the wall of the cell casing in a furtherflexed position.

FIG. 5A is a side view of the cell casing of another embodiment of theinvention.

FIG. 5B is a section view of the cell casing of FIG. 5A.

FIG. 6A is a section view of the wall of the cell casing in a non-flexedposition.

FIG. 6B is a section view of the wall of the cell casing of FIG. 6A in aflexed position.

FIG. 6C is a section view of the wall of the cell casing of FIG. 6A in afurther flexed position.

FIG. 7 is a section view of the wall of the cell casing of anotherembodiment of the invention in a non-flexed position.

FIG. 8A is a view of the first conductive plate of the battery of theinvention.

FIG. 8B is a top view of the first conductive plate of the battery ofthe invention.

FIG. 8C is a section view of the first conductive plate of FIG. 8B alongline AA.

DETAILED DESCRIPTION OF THE INVENTION

The foregoing will be apparent from the following more particulardescription of example embodiments of the invention, as illustrated inthe accompanying drawings. The drawings are not necessarily to scale,emphasis instead being placed upon illustrating embodiments of thepresent invention.

As used herein, the “terminals” of the batteries of the invention meanthe parts or surfaces of the batteries to which external electriccircuits are connected.

The batteries of the invention typically include a first terminal inelectrical communication with a first electrode, and a second terminalin electrical communication with a second electrode. The first andsecond electrodes are contained within the cell casing of a battery ofthe invention, for example, in a “jelly roll” form. The first terminalcan be either a positive terminal in electrical communication with apositive electrode of the battery, or a negative terminal in electricalcommunication with a negative electrode of the battery, and vice versafor the second terminal. Preferably, the first terminal is a negativeterminal in electrical communication with a negative electrode of thebattery, and the second terminal is a positive terminal in electricalcommunication with a positive electrode of the battery.

As used herein, the phrase “electrically connected” or “in electricalcommunication” means certain parts are in communication with each otherby flow of electrons through conductors, as opposed to electrochemicalcommunication which involves flow of ions, such as Li⁺, throughelectrolytes.

FIG. 1 shows an exploded view of battery 10 of one embodiment of theinvention, in perspective. Battery 10 includes first electrode 12 andsecond electrode 14. First electrode 12 is electrically connected tofeed-through device 16, which includes first component 18, which isproximal to first electrode 12, and second component 20, which is distalto first electrode 12. The electrodes 12, 14 are placed inside batterycan 22 that includes cell casing 24 and lid 26, i.e., internal space 28defined by cell casing 24 and lid 26. Cell casing 24 and lid 26 ofbattery 10 are in electrical communication with each other.

As used herein, the term “feed-through” includes any material or devicethat connects electrode 12 of battery 10, within internal space 28defined by cell casing 24 and lid 26, with a component of the batteryexternal to that defined internal space. Preferably, feed-through device16 extends through a pass-through hole defined by lid 26. Feed-throughdevice 16 also can pass through lid 26 without deformation, such asbending, twisting and/or folding, and can increase cell capacity. Onebenefit of using such a feed-through device includes a potentialincrease (e.g., 5-15%) in cell capacity due to increased volumeutilization, as compared to that of a conventional lithium battery inwhich current-carrying tabs are folded or bent into a cell casing andare welded with internal electrodes. Any other suitable means known inthe art can be used in the invention to connect electrode 12 with acomponent of the battery external to battery can 22, e.g., a terminal ofthe battery.

Cell casing 24 and lid 26 can be made of any suitable conductivematerial which is essentially stable electrically and chemically at agiven voltage of batteries, such as the lithium-ion batteries of theinvention. Examples of suitable materials of cell casing 24 includealuminum, nickel, copper, steel, nickel-plated iron, stainless steel andcombinations thereof. Preferably, cell casing 24 is of, or includes,aluminum. In a particularly preferred embodiment, cell casing 24 isformed of anodized aluminum. The aluminum of cell casing 24 can beanodized before, during or after shaping an aluminum blank to form cellcasing 24. Cell casing 24 can be labeled by any suitable method known inthe art, such as is described in U.S. Pat. No. 6,066,412 and WO00/11731, the teachings of which are incorporated herein by reference.In a preferred embodiment, where cell casing 24 is anodized, a label canbe formed on cell casing 24 by use of laser technology, as is known inthe art.

Examples of suitable materials of lid 26 are the same as those listedfor cell casing 24. Preferably lid 26 is made of the same material ascell casing 24. In a more preferable embodiment, both cell casing 24 andlid 26 are formed of, or include, aluminum. The aluminum of lid 26 canbe anodized. Lid 26 can hermetically seal cell casing 24 by any suitablemethod known in the art. Preferably, lid 26 and cell casing 24 arewelded to each other. Also, other forms of electrical connection of lid26 to cell casing 24 known in the art, such as crimping, can be employedin the invention.

Battery can 22, for example, lid 26, is electrically insulated fromfeed-through device 16, for example, by an insulating gasket (notshown). The insulating gasket is formed of a suitable insulatingmaterial, such as polypropylene, polyvinylfluoride (PVF), etc.

Cell casing 24 includes major surface 30, which is generally planarrelative to the remaining side surfaces of the casing, the remainingside surfaces typically being contoured such that a cross section of thecasing has an oblong shape. Cell casing 24 also includes substantiallyplanar recessed portion 32 of major surface area 30, and ridge sections36 on at least three sides of recessed portion 32. A remainder 38 ofmajor surface 30 surrounds recessed portion 32 and ridge portions 36,and is defined as the area of major surface 30 excluding recessedportion 32 and ridge portions 36.

In the embodiment shown in FIGS. 2A-2D, cell casing 24 is a 183665prismatic cell casing constructed of aluminum. The wall of cell casing24 is about 0.9 mm thick and a width defined by planes at opposing majorsurfaces of about 18.20 mm. As shown in FIG. 2B, recessed portion 32 hasa length of about 37 mm and a width of about 16 mm. At zero gaugepressure, the maximum depth of recessed portion 32 from remainder 38 ofmajor surface 30 is about 0.4 mm. Generally, recessed portion 32typically will occupy between about 10% and about 90% of generallyplanar major surface area 30. In the embodiment of the invention shownin FIG. 2B, ridge sections 36 border recessed portion 32 on three sidesof recessed portion 32.

FIGS. 2A and 2B show top and side views of cell casing 24, respectively.In one embodiment, recessed portion 32 has a length l of about 37 mm anda width w of about 16 mm. FIG. 2C shows a cross-sectional view of cellcasing 24 that shows the contours of one embodiment of the recessedportion 32 when the interior 28 of cell casing 24 is at about zerokilograms per square centimeter (kg/cm²). As used herein, the term“gauge pressure” refers to the difference between the absolute pressurein the battery casing interior and atmospheric pressure. FIG. 2D is adetail of FIG. 2C showing ridge section 36 of recessed portion 32.Recessed portion 32 can be formed by any suitable technique known in theart, such as rolling, stamping, etc.

In a preferred embodiment, recessed portion 32 is formed by use of anarbor 33 and punch 35, shown in FIGS. 3A and 3B, respectively. Arbor 33includes recess 37. When fabricating a cell casing, not shown, arbor 33is inserted within the cell casing from an open end of the cell casingso that end 33 a of arbor 33 proximates closed end 33 b of cell casing24, shown in FIGS. 2B and 2C. Punch 35, shown in FIG. 3B, is thenpressed into recess 37 at an end of recess 37 most proximate to the openend 33 c of cell casing 24, thereby forming recessed portion 32 of cellcasing 24. Punch 35, shown in FIG. 3B is then removed from cell casing24 and cell casing 24 can be removed from arbor 33. It is to beunderstood that, as a consequence of fabrication using arbor 33 andpunch 35, recessed portion 32 will be substantially planar and mergeinto remainder 38 at one end of recessed portion 32, thereby effectivelyresulting in cell casing 24 substantially as shown in FIG. 2. The shapeof cell casing 24 is formed by use of arbor 33 and punch 35 becauserecess 37 does not match punch 35, in that recess 37 is open on one sideto allow cell casing 24 to be removed from arbor 33. In other words,there is effectively no ridge along one side of recessed portion 32.

FIGS. 4A-4C are schematic cross-sectional representations of majorsurface area 30. FIG. 4A shows the major surface area in a non-flexedposition, which typifies the shape of the casing when the battery is notbeing charged, or has an internal gauge pressure when a batteryemploying the casing is not being charged.

Typically, the gauge pressure of a battery of the invention when notbeing charged (i.e., when not being introduced to an increase in gaugepressure) is less than about 5 kg/cm². As shown in FIG. 4A plane 31 a,defined by the boundary 72 between ridge section portions 36 andremainder 38 of major surface 30 is substantially aligned with thesurface of remainder 38 of major surface 30. This substantial alignmentgenerally defines the original position of the plane at a time prior toundergoing an increase in gauge pressure, which is represented by plane31 a.

When a battery of the invention is being charged, the gauge pressure canrise. As shown in FIG. 4B, when the gauge pressure of a battery of theinvention increases, the increase in gauge pressure causes the planedefined by the boundary 72 between ridge portions 36 and remainder 38 ofmajor surface 30 to move away from the original position.

In one embodiment, movement of the plane is a consequence of cooperationbetween recessed portion 32 and remainder 38 through ridge portions 36.As can be seen in FIG. 4B, flexing of recessed portion 32 forces ridgesections 36, and consequently its boundary 72 with remainder 38,outwardly, thereby moving the plane to a second position. Plane 31 brepresents the plane in the second position. In the embodiment shown inFIG. 4B, recessed portion 32 flexes during recharging to a point beyondplane 31 a, but still within plane 31 b.

In another embodiment, as shown in FIG. 4C, recessed portion 32 flexesduring recharging to a point beyond plane 31 b.

In another embodiment, as shown in FIGS. 5A-5B and 6A-6C, ridge portions36 surround recessed portion 32 on four sides rather than three sides,in contrast to the embodiment shown in FIGS. 2B, 2C, and 4A-4C.

In yet another embodiment, as shown in FIG. 7, ridge portions 36 ofgenerally planar major surface 30 has an arc shape, defined, forexample, by the radius of a circle. In such cases, the boundary 74between ridge portions 36 and recessed portion 32 is defined at thepoint of tangency of recessed portion 74 from the arc.

In all embodiments, the boundary 74 between ridge portions 36 andrecessed portion 32 remains recessed relative to the plane defined bythe boundary 72 between ridge portions 36 and remainder 38 up to a gaugepressure of at least 40 kg/cm². Also in all embodiments, recessedportion 32 preferably returns to essentially its original position afterrecharging is complete. In addition, the position of the plane prior toan increase in gauge pressure, i.e., plane 31 a, is substantially thesame as the position of the plane upon return of the gauge pressure froman increased level.

In one embodiment, the width W of cell casing 24, shown in FIG. 2A,extends from about 18.02 mm to no more than about 19.5 mm under a gaugepressure of about 12 kg/cm². In a specific embodiment, cell casing 24 isof anodized aluminum having a width W prior to flexing of about 18.02mm, and a width W after pressurizing to about 11.14 kg/cm² of betweenabout 18.4 mm and about 19.0 mm, whereas the same cell casing 24 ofaluminum, without anodization, will expand in width W from 18.02 mm to awidth W of between about 20.18 mm to about 20.40 mm. It is believed thatreducing flex of the battery casing, as in the present invention, causesthe gauge pressure to increase beyond what would occur during the samerecharging cycle of a typical cell casing, whereby the space required bythe battery is reduced, while still allowing the jelly roll of thebattery to expand during charging cycles, thereby preserving life of thebattery.

Returning to FIG. 1, at least one of cell casing 24 and lid 26 ofbattery can 22 are in electrical communication with second electrode 14of battery 10 through CID 40. Battery can 22, i.e., cell casing 24 andlid 26, is electrically insulated from a first terminal of battery 10,and at least a portion of battery can 22 is at least a component of asecond terminal of battery 10, or is electrically connected to thesecond terminal. In a preferred embodiment, at least a portion of lid 26or the bottom of cell casing 24 serves as a second terminal of battery10, and feed-through device 16 includes top conductive layer 26, whichcan serve as a first terminal of battery 10 in electrical communicationwith first electrode 12. First component 18, second component 20 and topconductive layer 26 each and independently can be made of any suitableconductive material known in the art, for example, nickel.

Battery 10 of the invention includes CID 40. Although one CID 40 isemployed in battery 10, more than one CID 40 can be employed in theinvention. CID 40 includes first conductive plate 42 and secondconductive plate 44 in electrical communication with each other (e.g.,by welding, crimping, riveting, etc.). Second conductive plate 44 is inelectrical communication with second electrode 14, and first conductiveplate 42 is in electrical contact with battery can 22, for example, lid26.

Preferably, the first conductive plate includes a frustum having anessentially planar cap. As shown in FIGS. 8A-8C, first conductive plate42 includes frustum 60 that includes first end 62 and second end 64.First end 62 has a broader diameter (indicated with reference character“j” in FIG. 4C) than the diameter of second end 64 (indicated withreference character “k” in FIG. 4C). First conductive plate 42 alsoincludes base 68 extending radially from a perimeter of first end 62 offrustum 60. Essentially planar cap 70 seals second end 64 of frustum 60.As used herein, the term “frustum” means the basal wall part (excludingthe bottom and top ends) of a solid right circular cone (i.e., solidgenerated by rotating a right triangle about one of its legs) by cuttingoff the top intersected between two parallel planes.

In CID 40, second conductive plate 44 separates from (e.g., deforms awayor is detached from) first conductive plate 42 when gauge pressureinside the battery is greater than a predetermined value, for example,between about 4 kg/cm² and about 15 kg/cm², or between about 5 kg/cm²and about 10 kg/cm², whereby a current flow between second electrode 14and battery can 22, at least a portion of which is at least a componentof a second terminal, or is electrically connected to the secondterminal, is interrupted.

Preferably, when second conductive plate 44 separates from firstconductive plate 42, no rupture occurs in second conductive plate 44 sothat gas inside battery 10 does not go out through second conductiveplate 44. The gas can exit battery 10 through one or more vent scores 46(e.g., at cell wall or the bottom part of cell casing 24, or secondconductive plate 44), which will be discussed later in detail, when theinternal pressure kept increasing and reaches a predetermined value foractivation of vent scores 46. In some embodiments, the predeterminedgauge pressure value for activation of vent scores 46, for example,between about 10 kg/cm² and about 20 kg/cm², is higher than that foractivation of CID 40, for example, between about 5 kg/cm² and about 10kg/cm². This feature helps prevent premature gas leakage, which candamage neighboring batteries (or cells) which are operating normally.So, when one of a plurality of cells in the battery packs of theinvention is damaged, the other healthy cells are not damaged. It isnoted that gauge pressure values or sub-ranges suitable for theactivation of CID 40 and those for activation of venting means 58 areselected from among the predetermined gauge pressure ranges such thatthere is no overlap between the selected pressure values or sub-ranges.Preferably, the values or ranges of gauge pressure for the activation ofCID 40 and those for the activation of venting means 58 differ by atleast about 2 kg/cm² pressure difference, more preferably by at leastabout 4 kg/cm², even more preferably by at least about 6 kg/cm², such asby about 7 kg/cm².

In a preferred embodiment, CID 40 further includes insulator 48 (e.g.,insulating layer or insulating gasket) between a portion of firstconductive plate 42 and second conductive plate 44. CID 40 is inelectrical communication with cell casing 24 of the battery. In CID 40,the second conductive plate 44 separates from (e.g., deforms away or isdetached from) the first conductive plate when pressure inside thebattery is greater than a predetermined value, for example, an internalgauge pressure in a range of between about 5 kg/cm² and about 10 kg/cm²,whereby a current flow between the second electrode and the secondterminal is interrupted.

In another preferred embodiment, at least one of first conductive plate42 and insulator 48 of CID 40 includes at least one hole (e.g., holes 50or 52 in FIG. 1) through which gas within battery 10 is in fluidcommunication with second conductive plate 44.

In a specific embodiment, CID 40 further includes end plate 54 disposedover first conductive plate 42, and defining at least one hole 56through which first conductive plate 42 is in fluid communication withthe atmosphere outside the battery. In a more specific embodiment, endplate 54 is a part of battery can 22, as shown in FIG. 1 where end plate54 is a part of lid 26 of battery can 22. In another more specificembodiment, end plate 54 is at battery can 22 of battery 10, forexample, over, under or at lid 26 of battery can 22, and in electricalcommunication with battery can 22.

CID 40 in the invention is placed within battery can 22, oralternatively, a portion of CID 40 is within battery can 22 and anotherportion of CID 40 is at or above battery can 22. Alternatively, CID 40can be electrically connected to lid 24 by any suitable means, such aswelding, crimping, etc. In a specific embodiment, at least one componentof CID 40, first and second conductive plates, 42, 44, insulator 48 andend plate 54, are positioned within battery can 22. In another specificembodiment, at least one component of CID 40, e.g., first and secondconductive plates, 42, 44, insulator 48, and end plate 54, is seatedwithin a recess at battery can 22, e.g., lid 24. In yet another specificembodiment, at least one of first and second conductive plates, 42, 44,and end plate 54, is a component of battery can 22, e.g., lid 24, orside or bottom of cell casing 22. In one more specific embodiment, atleast one of first and second conductive plates, 42, 44, and end plate54, is a portion of battery can 22, e.g., lid 24, or side or bottom ofcell casing 24. Even more specifically, at least one of first and secondconductive plates, 42, 44, and end plate 54, is coined or stamped at lid26, or the side or the bottom of cell casing 24, preferably at lid 54.In another more specific embodiment, end plate 54 is a part of lid 24(e.g., coined or stamped), and first and second conductive plates, 42,44, are placed within cell casing 24, as shown in FIG. 1.

First conductive plate 42 and second conductive plate 44 can be made ofany suitable conductive material known in the art for a battery.Examples of suitable materials include aluminum, nickel and copper,preferably aluminum. Preferably, battery can 22 (e.g., cell casing 24and lid 26), first conductive plate 42 and second conductive plate 44are made of substantially the same metals. As used herein, the term“substantially same metals” means metals that have substantially thesame chemical and electrochemical stability at a given voltage, e.g.,the operation voltage of a battery. More preferably, battery can 22,first conductive plate 42 and second conductive plate 44 are made of thesame metal, such as aluminum.

Cell casing 24 (e.g., the cell wall or the bottom part) includes atleast one venting means 58 as a means for venting internal space 28 whennecessary, such as when gauge pressure within lithium ion battery 10 isgreater than a value of between about 10 kg/cm² and about 20 kg/cm². Insome embodiments, second conductive plate 44 includes at least oneventing means, such as vent scores 46, although it is to be understoodthat any suitable type of venting means can be employed as long as themeans provide hermetic sealing in normal battery operation conditions.

As used herein, the term “score” means partial incision of section(s) ofa cell casing, such as cell casing 24, that is designed to allow thecell pressure and any internal cell components to be released at adefined internal gauge pressure, (e.g., between about 10 and about 20kg/cm²). Preferably, the vent score is directionally positioned awayfrom a user/or neighboring cells. As shown, more than one vent score canbe employed. In some embodiments, pattern vent scores can be employed.The vent score can be parallel, perpendicular, diagonal to a majorstretching (or drawing) direction of the cell casing material duringcreation of the shape of cell casing 24. Consideration is also given tovent score properties, such as depth, shape and length (size).

The batteries of the invention can further include a positive thermalcoefficient layer (PTC) in electrical communication with either thefirst terminal or the second terminal, preferably in electricalcommunication with the first terminal. Suitable PTC materials are thoseknown in the art. Generally, suitable PTC materials are those that, whenexposed to an electrical current in excess of a design threshold, itselectrical conductivity decreases with increasing temperature by severalorders of magnitude (e.g., 10⁴ to 10⁶ or more). Once the electricalcurrent is reduced below a suitable threshold, in general, the PTCmaterial substantially returns to the initial electrical resistivity. Inone suitable embodiment, the PTC material includes small quantities ofsemiconductor material in a polycrystalline ceramic, or a slice ofplastic or polymer with carbon grains embedded in it. When thetemperature of the PTC material reaches a critical point, thesemiconductor material or the plastic or polymer with embedded carbongrains forms a barrier to the flow of electricity and causes electricalresistance to increase precipitously. The temperature at whichelectrical resistivity precipitously increases can be varied byadjusting the composition of the PTC material, as is known in the art.An “operating temperature” of the PTC material is a temperature at whichthe PTC exhibits an electrical resistivity about half way between itshighest and lowest electrical resistance. Preferably, the operatingtemperature of the PTC layer employed in the invention is between about70° Celsius and about 150° Celsius.

Examples of specific PTC materials include polycrystalline ceramicscontaining small quantities of barium titanate (BaTiO₃), and polyolefinsincluding carbon grains embedded therein. Examples of commerciallyavailable PTC laminates that include a PTC layer sandwiched between twoconducting metal layers include LTP and LR4 series manufactured byRaychem Co. Generally, the PTC layer has a thickness in a range of about50 μm and about 300 μm.

Preferably, the PTC layer includes electrically conductive surface, thetotal area of which is at least about 25% or at least about 50% (e.g.,about 48% or about 56%) of the total surface area of lid 26 or thebottom of battery 10. The total surface area of the electricallyconductive surface of the PTC layer can be at least about 56% of thetotal surface area of lid 26 or the bottom of battery 10. Up to 100% ofthe total surface area of lid 26 of battery 10 can occupied by theelectrically conductive surface of the PTC layer. Alternatively, thewhole, or part, of the bottom of battery 10 can be occupied by theelectrically conductive surface of the PTC layer.

The PTC layer can be positioned internally or externally to the cell can(e.g., lid 22 or the bottom part of cell casing 24), preferablyexternally to the cell can, for example, over lid 26 of the cell can.

In a preferred embodiment, the PTC layer is between a first conductivelayer and a second conductive layer and at least a portion of the secondconductive layer is at least a component of the first terminal, or iselectrically connected to the first terminal. In a more preferredembodiment, the first conductive layer is connected to the feed-throughdevice. Suitable examples of such a PTC layer sandwiched between thefirst and second conductive layers are described in U.S. patentapplication Ser. No. 11/474,081, filed on Jun. 23, 2006, the entireteachings of which are incorporated herein by reference.

In some other embodiments, the cells or batteries of the invention areprismatic, as shown in FIG. 1 (stacked or wound, e.g., 183665 or 103450configuration). Preferably, the cells or batteries of the invention areof a prismatic shape that is oblong. Although the present invention canuse all types of prismatic cell casings, an oblong cell casing ispreferred partly due to the two features described below.

The available internal volume of an oblong shape, such as the 183665form factor, is larger than the volume of two 18650 cells, whencomparing stacks of the same external volume. When assembled into abattery pack, the oblong cell fully utilizes more of the space that isoccupied by the battery pack. This enables novel design changes to theinternal cell components that can increase key performance featureswithout sacrificing cell capacity relative to that found in the industrytoday. Due to the larger available volume, one can elect to use thinnerelectrodes, which have relatively higher cycle life and a higher ratecapability. Furthermore, an oblong can has larger flexibility. Forinstance, an oblong shape can flex more at the waist point compared to acylindrically shaped can, which allows less flexibility as stackpressure is increasing upon charging. The increased flexibilitydecreases mechanical fatigue on the electrodes, which, in turn, causeshigher cycle life. Also, clogging of pores of a separator in batteriescan be improved by the relatively lower stack pressure.

A particularly desired feature, allowing relatively higher safety, isavailable for the oblong shaped battery compared to the prismaticbattery. The oblong shape provides a snug fit to the jelly roll, whichminimizes the amount of electrolyte necessary for the battery. Therelatively lower amount of electrolyte results in less availablereactive material during a misuse scenario and hence higher safety. Inaddition, cost is lower due to a lower amount of electrolyte. In thecase of a prismatic can with a stacked electrode structure, whosecross-section is in a rectangular shape, full volume utilization ispossible without unnecessary electrolyte, but this type of can design ismore difficult and hence more costly from a manufacturing point-of-view.

Preferably, at least one cell has a prismatic shaped cell casing, andmore preferably, an oblong shaped cell casing, as shown in FIG. 1. Morepreferably, at least one cell has an 183665 configuration. Preferably,the capacity of the cells in the battery pack is typically equal to orgreater than about 3.0 Ah, more preferably equal to or greater thanabout 4.0 Ah. The internal impedance of the cells is preferably lessthan about 50 milliohms, and more preferably less than 30 milliohms.

The lithium-ion batteries and battery packs of the invention can be usedfor portable power devices, such as portable computers, power tools,toys, portable phones, camcorders, PDAs and the like. In the portableelectronic devices using lithium-ion batteries, their charges are, ingeneral, designed for a 4.20 V charging voltage. Thus, the lithium-ionbatteries and battery packs of the invention are particularly useful forthese portable electronic devices.

The present invention also includes methods of producing a battery, suchas a lithium-ion battery, as described above. The methods includeforming a cell casing as described above, and disposing a firstelectrode and a second electrode within the cell casing. A currentinterrupt device, as described above (e.g., current interrupt device28), is formed and electrically connected with the cell casing.

Positive and negative electrodes and electrolytes for the lithium-ionbatteries of the invention can be formed by suitable methods known inthe art.

Examples of suitable negative-active materials for the negativeelectrodes include any material allowing lithium to be doped or undopedin or from the material. Examples of such materials include carbonaceousmaterials, for example, non-graphitic carbon, artificial carbon,artificial graphite, natural graphite, pyrolytic carbons, cokes such aspitch coke, needle coke, petroleum coke, graphite, vitreous carbons, ora heat-treated organic polymer compounds obtained by carbonizing phenolresins, furan resins, or similar, carbon fibers, and activated carbon.Further, metallic lithium, lithium alloys, and an alloy or compoundthereof are usable as the negative active materials. In particular, themetal element or semiconductor element allowed to form an alloy orcompound with lithium may be a group IV metal element or semiconductorelement, such as but not limited to, silicon or tin. In particular,amorphous tin that is doped with a transition metal, such as cobalt oriron/nickel, is a metal that is suitable as an anode material in thesetypes of batteries. Oxides allowing lithium to be doped or undoped in orout from the oxide at a relatively basic potential, such as iron oxide,ruthenium oxide, molybdenum oxide, tungsten oxide, titanium oxide, andtin oxide, and nitrides, similarly, are usable as the negative-activematerials.

Suitable positive-active materials for the positive electrodes includeany material known in the art, for example, lithium nickelate (e.g.,Li_(1+x)NiM′O₂), lithium cobaltate (e.g., Li_(1+x)CoO₂), olivine-typecompounds (e.g., Li_(1+x)FePO₄), manganate spinel (e.g.,Li_(1+x9)Mn_(2−y9)O₄ (x9 and y9 are each independently equal to orgreater than zero and equal to or less than 0.3) orLi_(1+x1)(Mn_(1−y1)A′_(y2)2−x2)O_(z1)) (x1 and x2 are each independentlyequal to or greater than 0.01 and equal to or less than 0.3; y1 and y2are each independently equal to or greater than 0.0 and equal to or lessthan 0.3; z1 is equal to or greater than 3.9 and equal to or less than4.1), and mixtures thereof. Various examples of suitable positive-activematerials can be found in international application No.PCT/US2005/047383, filed on Dec. 23, 2005, U.S. patent application Ser.No. 11/485,068, file on Jul. 12, 2006, and International Application,filed on Jun. 22, 2007, entitled “Lithium-Ion Secondary Battery”, theentire teachings of all of which are incorporated herein by reference.

In one specific embodiment, the positive-active materials for thepositive electrodes of the invention include a lithium cobaltate, suchas Li_((1+x8))CoO_(z8). More specifically, a mixture of about 60-90 wt %(e.g. about 80 wt %) of a lithium cobaltate, such asLi_((1+x8))CoO_(z8), and about 40-10 wt % (e.g., about 20 wt %) of amanganate spinel (e.g., having about 100-115 mAh/g), such asLi_((1+x1))Mn₂O_(z1), preferably Li_((1+x1))Mn₂O₄, is employed for theinvention. The value x1 is equal to or greater than zero and equal to orless than 0.3 (e.g., 0.05≦x1≦0.15). The value z1 is equal to or greaterthan 3.9 and equal to or greater than 4.2. The value x8 is equal to orgreater than zero and equal to or less than 0.2. The value z8 is equalto or greater than 1.9 and equal to or greater than 2.1.

In another specific embodiment, the positive-active materials for theinvention include a mixture that includes a lithium cobaltate, such asLi_((1+x8))CoO_(z8), and a manganate spinel represented by an empiricalformula of Li_((1+x1))(Mn_(1−y1)A′_(y2))_(2−x2)O_(z1). The values x1 andx2 are each independently equal to or greater than 0.01 and equal to orless than 0.3. The values y1 and y2 are each independently equal to orgreater than 0.0 and equal to or less than 0.3. The value z1 is equal toor greater than 3.9 and equal to or less than 4.2. A′ is at least onemember of the group consisting of magnesium, aluminum, cobalt, nickeland chromium. More specifically, the lithium cobaltate and the manganatespinel are in a weight ratio of lithium cobaltate:manganate spinelbetween about 0.95:0.05 and about 0.9:0.1 to about 0.6:0.4.

In yet another specific embodiment, the positive-active materials forthe invention include a mixture that includes 100% of a lithiumcobaltate, such as Li_((1+x8))CoO_(z8).

In yet another specific embodiment, the positive-active materials forthe invention include at least one lithium oxide selected from the groupconsisting of: a) a lithium cobaltate; b) a lithium nickelate; c) amanganate spinel represented by an empirical formula ofLi_((1+x1))(Mn_(1−y1)A′_(y2))_(2−x2)O_(z1); d) a manganate spinelrepresented by an empirical formula of Li_((1+x1))Mn₂O_(z1) orLi_(1+x9)Mn_(2−y9)O₄; and e) an olivine compound represented by anempirical formula of Li_((1−x10))A″_(x10)MPO₄. The values of x1, z1, x9and y9 are as described above. The value, x2, is equal to or greaterthan 0.01 and equal to or less than 0.3. The values of y1 and y2 areeach independently equal to or greater than 0.0 and equal to or lessthan 0.3. A′ is at least one member of the group consisting ofmagnesium, aluminum, cobalt, nickel and chromium. The value, x10, isequal to or greater than 0.05 and equal to or less than 0.2, or thevalue, x10, is equal to or greater than 0.0 and equal to or less than0.1. M is at least one member of the group consisting of iron,manganese, cobalt and magnesium. A″ is at least one member of the groupconsisting of sodium, magnesium, calcium, potassium, nickel and niobium.

A lithium nickelate that can be used in the invention includes at leastone modifier of either the Li atom or Ni atom, or both. As used herein,a “modifier” means a substituent atom that occupies a site of the Liatom or Ni atom, or both, in a crystal structure of LiNiO₂. In oneembodiment, the lithium nickelate includes only a modifier of, orsubstituent for, Li atoms (“Li modifier”). In another embodiment, thelithium nickelate includes only a modifier of, or substituent for, Niatoms (“Ni modifier”). In yet another embodiment, the lithium nickelateincludes both the Li and Ni modifiers. Examples of Li modifiers includebarium (Ba), magnesium (Mg), calcium (Ca) and strontium (Sr). Examplesof Ni modifiers include those modifiers for Li and, in addition,aluminum (Al), manganese (Mn) and boron (B). Other examples of Nimodifiers include cobalt (Co) and titanium (Ti). Preferably, the lithiumnickelate is coated with LiCoO₂. The coating can be, for example, agradient coating or a spot-wise coating.

One particular type of a lithium nickelate that can be used in theinvention is represented by an empirical formula ofLi_(x3)Ni_(1−z3)M′_(z3)O₂ where 0.05<x3<1.2 and 0<z3<0.5, and M′ is oneor more elements selected from a group consisting of Co, Mn, Al, B, Ti,Mg, Ca and Sr. Preferably, M′ is one or more elements selected from agroup consisting of Mn, Al, B, Ti, Mg, Ca and Sr.

Another particular type of a lithium nickelate that can be used in theinvention is represented by an empirical formula ofLi_(x4)A*_(x5)Ni_((1−y4−z4))Co_(y4)Q_(z4)O_(a) where x4 is equal to orgreater than about 0.1 and equal to or less than about 1.3; x5 is equalto or greater than 0.0 and equal to or less than about 0.2; 4 is equalto or greater than 0.0 and equal to or less than about 0.2; z4 is equalto or greater than 0.0 and equal to or less than about 0.2; a is greaterthan about 1.5 and less than about 2.1; A* is at least one member of thegroup consisting of barium (Ba), magnesium (Mg) and calcium (Ca); and Qis at least one member of the group consisting of aluminum (Al),manganese (Mn) and boron (B). Preferably, 4 is greater than zero. In onepreferred embodiment, x5 is equal to zero, and z4 is greater than 0.0and equal to or less than about 0.2. In another embodiment, z4 is equalto zero, and x5 is greater than 0.0 and equal to or less than about 0.2.In yet another embodiment, x5 and z4 are each independently greater than0.0 and equal to or less than about 0.2. In yet another embodiment, x5,y4 and z4 are each independently greater than 0.0 and equal to or lessthan about 0.2. Various examples of lithium nickelates where x5, y4 andz4 are each independently greater than 0.0 and equal to or less thanabout 0.2, can be found in U.S. Pat. Nos. 6,855,461 and 6,921,609 (theentire teachings of which are incorporated herein by reference).

A specific example of the lithium nickelate isLiNi_(0.8)Co_(0.15)Al_(0.05)O₂. A preferred specific example isLiCoO₂-coated LiNi_(0.8)Co_(0.15)Al_(0.05)O₂. In a spot-wise coatedcathode, LiCoO₂ doe not fully coat the nickelate core particle. Thecomposition of LiNi_(0.8)Co_(0.15)Al_(0.05)O₂ coated with LiCoO₂ cannaturally deviate slightly in composition from the 0.8:0.15:0.05 weightratio between Ni:Co:Al. The deviation can range about 10-15% for the Ni,5-10% for Co and 2-4% for Al. Another specific example of the lithiumnickelate is Li_(0.97)Mg_(0.03)Ni_(0.9)Co_(0.1)O₂. A preferred specificexample is LiCoO₂-coated Li_(0.97)Mg_(0.03)Ni_(0.9)Co_(0.1)O₂. Thecomposition of Li_(0.97)Mg_(0.03)Ni_(0.9)Co_(0.1)O₂ coated with LiCoO₂can deviate slightly in composition from the 0.03:0.9:0.1 weight ratiobetween Mg:Ni:Co. The deviation can range about 2-4% for Mg, 10-15% forNi and 5-10% for Co. Another preferred nickelate that can be used in thepresent invention is Li(Ni_(1/3)Co_(1/3)Mn_(1/3))O₂, also called“333-type nickelate.” This 333-type nickelate optionally can be coatedwith LiCoO₂, as described above.

Suitable examples of lithium cobaltates that can be used in theinvention include Li_(1+x8)CoO₂ that is modified by at least one of Lior Co atoms. Examples of the Li modifiers are as described above for Liof lithium nickelates. Examples of the Co modifiers include themodifiers for Li and aluminum (Al), manganese (Mn) and boron (B). Otherexamples include nickel (Ni) and titanium (Ti) and, in particular,lithium cobaltates represented by an empirical formula ofLi_(x6)M′_(y6)Co_((1−z6))M″_(z6)O₂, where x6 is greater than 0.05 andless than 1.2; y6 is greater than 0 and less than 0.1, z6 is equal to orgreater than 0 and less than 0.5; M′ is at least one member of magnesium(Mg) and sodium (Na) and M″ is at least one member of the groupconsisting of manganese (Mn), aluminum (Al), boron (B), titanium (Ti),magnesium (Mg), calcium (Ca) and strontium (Sr), can be used in theinvention. Another example of a lithium cobaltate that can be used inthe invention is unmodified Li_(1+x8)CoO₂, such as LiCoO₂. In onespecific embodiment, the lithium cobaltate (e.g., LiCoO₂) doped with Mgand/or coated with a refractive oxide or phosphate, such as ZrO₂ orAl(PO₄).

It is particularly preferred that lithium oxide compounds employed havea spherical-like morphology, since it is believed that this improvespacking and other production-related characteristics.

Preferably, a crystal structure of each of the lithium cobaltate andlithium nickelate is independently a R-3m type space group(rhombohedral, including distorted rhombohedral). Alternatively, acrystal structure of the lithium nickelate can be in a monoclinic spacegroup (e.g., P2/m or C2/m). In a R-3m type space group, the lithium ionoccupies the “3a” site (x=0, y=0 and z=0) and the transition metal ion(i.e., Ni in a lithium nickelate and Co in a lithium cobaltate) occupiesthe “3b” site (x=0, y=0, z=0.5). Oxygen is located in the “6a” site(x=0, y=0, z=z0, where z0 varies depending upon the nature of the metalions, including modifier(s) thereof).

Examples of olivine compounds that are suitable for use in the inventionare generally represented by a general formula Li_(1−x2)A″_(x2)MPO₄,where x2 is equal to or greater than 0.05, or x2 is equal to or greaterthan 0.0 and equal to or greater than 0.1; M is one or more elementsselected from a group consisting of Fe, Mn, Co, or Mg; and A″ isselected from a group consisting of Na, Mg, Ca, K, Ni, Nb. Preferably, Mis Fe or Mn. More preferably, LiFePO₄ or LiMnPO₄, or both are used inthe invention. In a preferred embodiment, the olivine compounds arecoated with a material having relatively high electrical conductivity,such as carbon. In a more preferred embodiment, carbon-coated LiFePO₄ orcarbon-coated LiMnPO₄ is employed in the invention. Various examples ofolivine compounds where M is Fe or Mn can be found in U.S. Pat. No.5,910,382 (the entire teachings of which are incorporated herein byreference).

The olivine compounds typically have a small change in crystal structureupon charging/discharging, which generally makes the olivine compoundssuperior in terms of cycle characteristics. Also, safety is generallyhigh, even when a battery is exposed to a high temperature environment.Another advantage of olivine compounds (e.g., LiFePO₄ and LiMnPO₄) istheir relatively low cost.

Manganate spinel compounds have a manganese base, such as LiMn₂O₄. Whilethe manganate spinel compounds typically have relatively low specificcapacity (e.g., in a range of about 110 to 115 mAh/g), they haverelatively high power delivery when formulated into electrodes andtypically are safe in terms of chemical reactivity at highertemperatures. Another advantage of the manganate spinel compounds istheir relatively low cost.

One type of manganate spinel compounds that can be used in the inventionis represented by an empirical formula ofLi_((1+x1))(Mn_(1−y1)A′_(y2))_(2−x2)O_(z1), where A′ is one or more ofMg, Al, Co, Ni and Cr; x1 and x2 are each independently equal to orgreater than 0.01 and equal to or less than 0.3; y1 and y2 are eachindependently equal to or greater than 0.0 and equal to or less than0.3; z1 is equal to or greater than 3.9 and equal to or less than 4.1.Preferably, A′ includes a M³⁺ ion, such as Al³⁺, Co³⁺, Ni³⁺ and Cr³⁺,more preferably Al³⁺. The manganate spinel compounds ofLi_((1+x1))(Mn_(1−y1)A′_(y2))_(2−x2)O_(z1) can have enhanced cyclabilityand power compared to those of LiMn₂O₄. Another type of manganate spinelcompounds that can be used in the invention is represented by anempirical formula of Li_((1+x1))Mn₂O_(z1), where x1 and z1 are eachindependently the same as described above. Alternatively, the manganatespinel for the invention includes a compound represented by an empiricalformula of Li_(1+x9)Mn_(2−y9)O_(z9) where x9 and y9 are eachindependently equal to or greater than 0.0 and equal to or less than 0.3(e.g., 0.05≦x9, y9≦0.15); and z9 is equal to or greater than 3.9 andequal to or less than 4.2. Specific examples of the manganate spinelthat can be used in the invention include LiMn_(1.9)Al_(0.1)O₄,Li_(1+x1)Mn₂O₄, Li_(1+x7)Mn_(2−y7)O₄ and their variations with Al and Mgmodifiers. Various other examples of manganate spinel compounds of thetype Li_((1+x1))(Mn_(1−y1)A′_(y2))_(2−x2)O_(z1) can be found in U.S.Pat. Nos. 4,366,215; 5,196,270; and 5,316,877 (the entire teachings ofwhich are incorporated herein by reference).

It is noted that the suitable cathode materials described herein arecharacterized by empirical formulas that exist upon manufacture oflithium-ion batteries in which they are incorporated. It is understoodthat their specific compositions thereafter are subject to variationpursuant to their electrochemical reactions that occur during use (e.g.,charging and discharging).

Examples of suitable non-aqueous electrolytes include a non-aqueouselectrolytic solution prepared by dissolving an electrolyte salt in anon-aqueous solvent, a solid electrolyte (inorganic electrolyte orpolymer electrolyte containing an electrolyte salt), and a solid orgel-like electrolyte prepared by mixing or dissolving an electrolyte ina polymer compound or the like.

The non-aqueous electrolytic solution is typically prepared bydissolving a salt in an organic solvent. The organic solvent can includeany suitable type that has been generally used for batteries of thistype. Examples of such organic solvents include propylene carbonate(PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethylcarbonate (DMC), 1,2-dimethoxyethane, 1,2-diethoxyethane,γ-butyrolactone, tetrahydrofuran, 2-methyl tetrahydrofuran,1,3-dioxolane, 4-methyl-1,3-dioxolane, diethyl ether, sulfolane,methylsulfolane, acetonitrile, propionitrile, anisole, acetate,butyrate, propionate and the like. It is preferred to use cycliccarbonates such as propylene carbonate, or chain carbonates such asdimethyl carbonate and diethyl carbonate. These organic solvents can beused singly or in a combination of two types or more.

Additives or stabilizers may also be present in the electrolyte, such asVC (vinyl carbonate), VEC (vinyl ethylene carbonate), EA (ethyleneacetate), TPP (triphenylphosphate), phosphazenes, biphenyl (BP),cyclohexylbenzene (CHB), 2,2-diphenylpropane (DP), lithiumbis(oxalato)borate (LiBoB), ethylene sulfate (ES) and propylene sulfate.These additives are used as anode and cathode stabilizers, flameretardants or gas releasing agents, which may make a battery have higherperformance in terms of formation, cycle efficiency, safety and life.

The solid electrolyte can include an inorganic electrolyte, a polymerelectrolyte and the like insofar as the material has lithium-ionconductivity. The inorganic electrolyte can include, for example,lithium nitride, lithium iodide and the like. The polymer electrolyte iscomposed of an electrolyte salt and a polymer compound in which theelectrolyte salt is dissolved. Examples of the polymer compounds usedfor the polymer electrolyte include ether-based polymers such aspolyethylene oxide and cross-linked polyethylene oxide, polymethacrylateester-based polymers, acrylate-based polymers and the like. Thesepolymers may be used singly, or in the form of a mixture or a copolymerof two kinds or more.

A matrix of the gel electrolyte may be any polymer insofar as thepolymer is gelated by absorbing the above-described non-aqueouselectrolytic solution. Examples of the polymers used for the gelelectrolyte include fluorocarbon polymers such as polyvinylidenefluoride (PVDF), polyvinylidene-co-hexafluoropropylene (PVDF-HFP) andthe like.

Examples of the polymers used for the gel electrolyte also includepolyacrylonitrile and a copolymer of polyacrylonitrile. Examples ofmonomers (vinyl based monomers) used for copolymerization include vinylacetate, methyl methacrylate, butyl methacylate, methyl acrylate, butylacrylate, itaconic acid, hydrogenated methyl acrylate, hydrogenatedethyl acrylate, acrlyamide, vinyl chloride, vinylidene fluoride, andvinylidene chloride. Examples of the polymers used for the gelelectrolyte further include acrylonitrile-butadiene copolymer rubber,acrylonitrile-butadiene-styrene copolymer resin,acrylonitrile-chlorinated polyethylene-propylenediene-styrene copolymerresin, acrylonitrile-vinyl chloride copolymer resin,acrylonitrile-methacylate resin, and acrlylonitrile-acrylate copolymerresin.

Examples of the polymers used for the gel electrolyte include etherbased polymers such as polyethylene oxide, copolymer of polyethyleneoxide, and cross-linked polyethylene oxide. Examples of monomers usedfor copolymerization include polypropylene oxide, methyl methacrylate,butyl methacylate, methyl acrylate, butyl acrylate.

In particular, from the viewpoint of oxidation-reduction stability, afluorocarbon polymer is preferably used for the matrix of the gelelectrolyte.

The electrolyte salt used in the electrolyte may be any electrolyte saltsuitable for batteries of this type. Examples of the electrolyte saltsinclude LiClO₄, LiAsF₆, LiPF₆, LiBF₄, LiB(C₆H₅)₄, LiB(C₂O₄)₂, CH₃SO₃Li,CF₃SO₃Li, LiCl, LiBr and the like. Generally, a separator separates thepositive electrode from the negative electrode of the batteries. Theseparator can include any film-like material having been generally usedfor forming separators of non-aqueous electrolyte secondary batteries ofthis type, for example, a microporous polymer film made frompolypropylene, polyethylene, or a layered combination of the two. Inaddition, if a solid electrolyte or gel electrolyte is used as theelectrolyte of the battery, the separator does not necessarily need tobe provided. A microporous separator made of glass fiber or cellulosematerial can in certain cases also be used. Separator thickness istypically between 9 and 25 μm.

In some specific embodiments, a positive electrode can be produced bymixing the cathode powders at a specific ratio. 90 wt % of this blend isthen mixed together with 5 wt % of acetylene black as a conductiveagent, and 5 wt % of PVDF as a binder. The mix is dispersed inN-methyl-2-pyrrolidone (NMP) as a solvent, in order to prepare slurry.This slurry is then applied to both surfaces of an aluminum currentcollector foil, having a typical thickness of about 20 um, and dried atabout 100-150° C. The dried electrode is then calendared by a rollpress, to obtain a compressed positive electrode. When LiCoO₂ is solelyused as the positive electrode a mixture using 94 wt % LiCoO₂, 3%acetylene black, and 3% PVDF is typically used. A negative electrode canbe prepared by mixing 93 Wt % of graphite as a negative active material,3 wt % acetylene black, and 4 wt % of PVDF as a binder. The negative mixwas also dispersed in N-methyl-2-pyrrolidone as a solvent, in order toprepare the slurry. The negative mix slurry was uniformly applied onboth surfaces of a strip-like copper negative current collector foil,having a typical thickness of about 10 um. The dried electrode is thencalendared by a roll press to obtain a dense negative electrode.

The negative and positive electrodes and a separator formed of apolyethylene film with micro pores, of thickness 25 um, are generallylaminated and spirally wound to produce a spiral type electrode element.

In some embodiments, one or more positive lead strips, made of, e.g.,aluminum, are attached to the positive current electrode, and thenelectrically connected to the positive terminal of the batteries of theinvention. A negative lead, made of, e.g., nickel metal, connects thenegative electrode, and then attached to a feed-through device, such asfeed-through device 16. An electrolyte of for instance EC:DMC:DEC with1M LiPF₆, is vacuum filled in the cell casing of a lithium-ion batteryof the invention, where the cell casing has the spirally wound “jellyroll.”

EQUIVALENTS

While this invention has been particularly shown and described withreferences to preferred embodiments thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the scope of the inventionencompassed by the appended claims.

What is claimed is:
 1. A battery casing having a recessed portion on amajor surface of the casing, the recessed portion being planar andbordering a remainder of the major surface at ridge portions on onlythree sides of the recessed portion and having a fourth side borderingthe remainder, wherein the ratio of a) the percent surface area of therecessed portion relative to the total surface area of a generallyplanar surface: b) the depth of the recessed portion relative to thewidth of the battery casing, is in a range of between about 5:1 andabout 45:1, whereby the recessed portion, the ridge portions, and theremainder of the major surface configured to cooperate under an increaseof gauge pressure to cause a plane defined by a boundary between theridge portions and the remainder of the major surface to move.
 2. Thebattery casing of claim 1, wherein at least a portion of the recessedportion is configured to flex under the increase of gauge pressure to apoint beyond a position of the plane prior to the increase of gaugepressure, and wherein a boundary between the ridge portion and therecessed portion remains recessed relative to the plane defined by theboundary between the ridge portions and remainder of the major plane upto a gauge pressure of at least 2 kg/cm².
 3. The battery casing of claim1, wherein at least a portion of the recessed portion is configured toflex under the increase of gauge pressure to a point beyond a positionof the plane during the increase of gauge pressure, and wherein aboundary between the ridge portion and the recessed portion remainsrecessed relative to the plane defined by the boundary between the ridgeportions and remainder of the major plane up to a gauge pressure of atleast 4 kg/cm².
 4. The battery casing of claim 3, wherein the casing isconstructed of a material that will cause the recessed portion to returnsubstantially to its initial shape and position relative to the planeupon return of the gauge pressure from an increased level.
 5. Thebattery casing of claim 1, wherein the casing is constructed of amaterial that will cause the position of the plane prior to the increaseof gauge pressure to be substantially the same as the position of theplane upon return of the gauge pressure from an increased level.
 6. Thebattery casing of claim 5, wherein the casing is constructed of at leastone material selected from the group consisting of aluminum, nickel,copper, steel, nickel plated iron and stainless steel.
 7. The batterycasing of claim 6, wherein the battery casing is a prismatic batterycasing.
 8. The battery casing of claim 7, wherein the prismatic batterycasing is an oblong prismatic battery cell casing.
 9. The battery cellcasing of claim 8, wherein the prismatic battery casing has dimensionsof 36 mm×65 mm×18 mm.
 10. The battery cell casing of claim 8, whereincasing is constructed of aluminum, and wherein the aluminum is anodized.11. The battery cell casing of claim 10, wherein the recessed portionoccupies between about 10% and about 90% of the major surface, the majorsurface being a generally planar portion of the cell casing.
 12. Thebattery cell casing of claim 11, wherein a most recessed point of therecessed portion is recessed from the plane defined by the boundarybetween the ridge portion and the remainder of the major surface in arange of between about 0.2 mm and about 0.6 mm at about zero kg/cm²gauge pressure.
 13. The battery casing of claim 12, wherein the recessedportion has a surface area, in a range of between about 500 mm² andabout 700 mm².